How many things cause cancer according to science studies? Probably the same amount of things that can make you magically healthy. What is good for you is bad for you is good for you, depending on the day and which scientific study came out recently. There are so many of those studies and they all prove and disprove each other that it's hard to figure out what's the truth anymore. Why is it like that?

Because of how the studies are conducted. Ted-Ed explains how clinical trials and epidemiological studies are flawed and why correlation is definitely not the same thing as causation. So next time you hear in the news that using toothpaste is bad for your liver or something crazy like that, you might want to dig deeper into the study.